Co-Pt bimetallic catalysts for the selective oxidation of carbon monoxide in hydrogen-containing mixtures

The performance of a Co-Pt powder and of Co-Pt catalysts supported on γ-Al₂O₃ and on the graphite-like carbon material Sibunit in selective CO oxidation in hydrogen-containing mixtures is considered. Fine particles of metal-metal solid solutions and intermetallides were obtained by the decomposition of a Co- and Pt-containing double complex salt in a hydrogen atmosphere at ～400°C. As compared to their Pt and Co monometallic counterparts, the bimetallic catalysts are more active and allow the CO concentration in hydrogen-containing mixtures to be reduced from 1 to 10^?3 vol %. This effect is likely due to the formation of bimetallic particles of a Co-Pt solid solution on the support surface.     

Copper-cerium oxide catalysts for the selective oxidation of carbon monoxide in hydrogen-containing mixtures: II. Physicochemical characterization of the catalysts

The copper-cerium oxide catalysts were characterized using a set of physicochemical techniques including in situ FTIR spectroscopy, XPS, and XRD. It was found that copper segregated on the surface of cerium oxide and its states were labile and dependent on catalyst pretreatment conditions. Copper in a dispersed state was responsible for the reaction of CO oxidation in the presence of H₂ on the copper-cerium oxide catalysts. It is likely that this state of copper was composed of two-dimensional or three-dimensional surface clusters containing Cu⁺ ions.     

Selective methanation of CO in the presence of CO<Subscript>2</Subscript> in hydrogen-containing mixtures on nickel catalysts

The screening of commercial nickel catalysts for methanation and a series of nickel catalysts supported on CeO₂, γ-Al₂O₃, and ZrO₂ in the reaction of selective CO methanation in the presence of CO₂ in hydrogen-containing mixtures (1.5 vol % CO, 20 vol % CO₂, 10 vol % H₂O, and the balance H₂) was performed at the flow rate WHSV = 26000 cm³ (g Cat)⁻¹ h⁻¹. It was found that commercial catalytic systems like NKM-2A and NKM-4A (NIAP-07-02) were insufficiently effective for the selective removal of CO to a level of <100 ppm. The most promising catalyst is 2 wt % Ni/CeO₂. This catalyst decreased the concentration of CO from 1.5 vol % to 100 ppm in the presence of 20 vol % CO₂ in the temperature range of 280–360°C at a selectivity of >40%, and it retained its activity even after contact with air. The minimum outlet CO concentration of 10 ppm at 80% selectivity on a 2 wt % Ni/CeO₂ catalyst was reached at a temperature of 300°C.     

Bimetallic Pt<Subscript>0.5</Subscript>Co<Subscript>0.5</Subscript>/SiO<Subscript>2</Subscript> Catalyst: Preparation,Structure, and Properties in Preferential Oxidation of Carbon Monoxide

The Pt_0.5Со_0.5/SiO₂ catalyst has been prepared by the decomposition of a [Pt(NH₃)₄][Co(C₂O₄)₂(H₂O)₂]. 2H₂O binary complex salt supported in the pores of SiO₂ pellets. It has been shown by a complex of physical and chemical methods that Pt_0.5Со_0.5/SiO₂ contains alloy nanoparticles with an average composition Pt0.5Co0.5. The catalytic properties of Pt_0.5Со_0.5/SiO₂ are studied in the preferential oxidation of СО in the reaction mixtures with various compositions. It was found that Pt_0.5Со_0.5/SiO₂ has a high selectivity and makes it possible to decrease the outlet concentration of CO to a level of <10 ppm, and the presence of СО₂ and/or Н₂О in the reaction mixture almost does not affect its catalytic properties. The structure of the catalyst is stable under the conditions of preferential CO oxidation.     

Copper-cerium oxide catalysts for the selective oxidation of carbon monoxide in hydrogen-containing mixtures: I. Catalytic activity

A series of copper-cerium oxide catalysts were prepared, and their properties toward the reaction of CO oxidation in hydrogen-containing gas mixtures were studied. It was found that the copper-cerium oxide catalysts are stable, active, and selective in this reaction. The conditions under which these catalysts decreased the concentration of CO from 1 to <10^?3 vol % in hydrogen containing water vapor and carbon dioxide were determined.     

The properties of carbon-carbonic condensate synthesized in the plasma arc

Physical and chemical properties of carbon-carbonic condensate synthesized by the plasma-arc technology have been studied experimentally. X-ray phase analysis has been performed, the isotherms of physical adsorption and sorption ability of the synthesized material have been measured. It has been concluded that this material offers promise as a carrier of catalytic nanoparticles and effective sorbent.     

Kinetic model and mechanism of the selective oxidation of CO in the presence of hydrogen on platinum catalysts

The reaction kinetics of the selective oxidation of carbon monoxide in the presence of hydrogen on a Pt/carbon support catalyst was studied. It was found that this catalyst exhibited high activity and decreased the concentration of CO in a hydrogen-containing gas from 0.6–1.0 vol % to less than 10 ppm at the inlet concentration ratio O₂/CO = 1.0–1.5. A kinetic model of the reaction was proposed to describe quantitatively the experimental results.     

Interaction between 193-nm pulsed laser radiation and α-alumina

The threshold power density of 15-ns laser pulses with a wavelength 193 nm is determined for basic modes of interaction between the radiation and α-alumina. As power density Q on the target varying in the range 0.001–100 MW/cm² increases, first the interaction mechanism changes from single-photon interaction to two-photon interaction at Q ≈ 0.1 MW/cm². At Q ≈ 5 MW/cm², the material sublimates and then the sublimation products ionize at Q ≈ 15 MW/cm². At Q ≈ 100 MW/cm², the material is removed from the surface at a rate of ≈ 10 nm per pulse.     

Bimetallic Rh-Co/ZrO<Subscript>2</Subscript> catalysts for ethanol steam reforming into hydrogen-containing gas

The properties of supported bimetallic Rh-Co/ZrO₂ catalysts in ethanol steam reforming into hydrogen-containing gas were studied. The particles of Rh-Co solid solutions on the catalyst surface were prepared by the thermal decomposition of the double complex salt [Co(NH₃)₆][Rh(NO₂)₆] and the solid solution Na₃[RhCo(NO₂)₆]. It was found that the bimetallic Rh-Co/ZrO₂ catalysts exhibited high activity in the reaction of ethanol steam reforming. The equilibrium composition of reaction products was attained at 500–700°C and a reaction mixture space velocity of 10000 h⁻¹.     

Autocatalytic gas-phase ethane dehydrogenation in a wall-less reactor

The thermal gas-phase pyrolysis of ethane was studied under conditions of the bulk heating of the reaction mixture with IR-laser radiation. The concentrations of ethane pyrolysis products as functions of reaction time were calculated in accordance with standard kinetic schemes; they showed that a classical radical chain mechanism corresponded to only highly dilute mixtures of ethane with an inert gas. As found by calculations, the experimental data on the kinetics of consumption of the initial substance and on the kinetics of buildup of pyrolysis products in undiluted mixtures of ethane and its conversion products were adequately described by an autocatalytic (with respect to ethylene) mechanism of ethane dehydrogenation. This mechanism involved the step of ethane interaction with ethylene to form methyl and propyl radicals.